Aqueous treatment of artificial silk



Patented'oct. 30. 1934 PATENT OFFICE mam AQUEOUS TREATMENT (I ARTIFICIALArchibald .Idm mu, 'Iimbenbrook, England, aaignor to CelaneeeCorporation of America, a

corporation of Delaware No Original application July 2:, 1925, SerialNo. 45,416. Divided and this application December 24, 1920', Serial No.416,305. In Great Britain my :1, m4

3 Claims.

This invention relates to the treatment of cellulose acetate productswith hot or boiling aqueous liquors and is a division of my Patent No.1,765,581, dated June 24, 1930.

It 'is well known that when cellulose acetate artificial silk isimmersed in boiling water or water whose temperature exceeds about 850., it becomes curly and wool-like and loses a considerable proportionof its lustre and transparency. I have now discovered, and thisdiscovery forms the basis of this invention, that the resistance againstdelustring of such silk ,when

heated at about 100 C., for prolonged periods i in the presence ofwater, is increased by the presenceof soluble salts of sodium.

Generallythe protective power of sodium salts is greater in concentratedaqueous solution than in dilute solution. For example cellulose acetatesilk becomes woolly and opaque and loses most of its lustre when heatedfor three minutes in boiling water, but retains its original appearanceand properties when heated for one hour at 100 C., in an aqueoussolution containing 12% of sodium chloride or 25% of crystalline sodiumsulphate. vOn the other hand cellulose acetate silk similarly heated forone hour at about 100 0., in an aqueous solution containing 5% of,sodium chloride becomes somewhat woolly and suffers a partial loss oflustre and transparency.

The following are examples of suitable sodium,

salts for use as protective substances towards cellulose acetateartificial silk:

Salt.

Sodium bichromate Sodium sulphite Sodium phosphate (di-basic) Sodiumnitrite Sodium bisulphite Sodium acetate Sodium thiosulphate Sodiumferrocyanide Sodium chlorate Sodium nitrate Sodium bromideSodium'chloride Sodium sulphate Sodium hydrosulphite Sodium tartrate Allthe above substances exert their protective action for cellulose acetatewhen used in from 10% to 30% aqueous solution, but it is understood thatthese limits of concentration are only stated approximately, and thefollowing table gives the approximate value of concentration for severalof the substances.

Among numerous processes in which my discovery has useful applicationsare; the dyeing in boiling liquors of fabrics containing celluloseacetate and woollen fibres, the discharging of dyed cellulose acetatefabrics in boiling liquors, and the relief or production of latentstrains in cellulose acetate fabrics or products by immersion in aboiling aqueous liquor.

What I claim and desire to secure by Letters Patent is:.-

1. In the treatment of textile materials, films and like materialscomprising cellulose acetate by processes which are without substantialeffect on the chemical character of the materials, which processescomprise treatments with aqueous media at temperatures in excess ofabout 85 C., the step of preventing loss of lustre of the materialswhich comprises carrying out such treatments in the presence of a sodiumsalt of a water soluble acid, which salt is chemically inert withrespect to the cellulose acetate, in aqueous solution in at least 10%concentration.

2. In the treatment of textile materials, films and like materialscomprising cellulose acetate by processes which are without substantialeffect on the chemical character of the materials, which processescomprise treatments with aqueous -media 'at boiling temperature, thestep of preventing loss of lustre of the materials which comprisescarrying out such treatments in the presence of a sodium salt of a watersoluble acid, which salt is chemically inert with respect to the act.

0., the step of preventingloss of lustre of the materials whichcomprises carrying out such treatments in the presence of a sodium saltof a water soluble acid, which salt is chemically inert with respect tothe cellulose acetate, in aqueous solution of 10-30% concentration.

ARCmBALD JOHN HALL.

